Safety system for alternating-current generators



W. GAARZ SAFETY SYSTEM FOR ALTERNYATING CURRENT GENERATORS.

June 2,

Filed Feb. '5, 1925 INVENTOR Mme/m aarz BY ATTORNEY Patented 1.... 2,192 1,539,834

UNITED STATES PATENT! OFFICE.

wrnnnmr GAARZ, or nnanm-cmnorrnnnm, enmmnr, ASSIGNOR 'ro wns'rmenousn nnncrmc a muracrunme comm, or new YORK, N. Y., a con.-

rona'rron.

SAFETY SYSTEM FORALTERNATING-CUBRENT GENERATORS. A Application filed February 3, 1925. Serial No. 6,60%. v

To all whom it may concern: the transformer 2 and the grounded shell Be it known that I, WILHELM GAARZ, a of the generator with the connecting point citizen of the German Empire, residing at 6 are connected with a common point Berlin-Charlottenburg, Germany, have inacross the resistances 7, 8 and 9 respective- 65 5 vented certain new and useful Improve- 1y. Between the point 10 and the neutral ments in Safety Systems for Alternating point of the transformer 5 is located the Current Generators, of which the followprimary coil 11 of a voltage transformer, ing is a specification. the secondary coil 12 of which operates a My invention relates to improvements in relay 13. In order that according to my 60 19 protective systems for alternating current invention the relay should only respond to generators. a limited frequency range around the nor- A protective system for. alternating curmal frequency of the network, for instance rent generators is already known in which at the standard frequency of 50 at fr the'neutral point of the generator is .conquencies of about 40 to 60, the circuit of 65 nected across a directly or indirectly conthe voltagerelay 13 is in the illustrated exnected relay with the primary neutral point ample shown as a resonance circuit. For,

of a bank of transformers connected with this purpose a condenser 14: and a chokthe generator or with the neutral point of ing coil 15 are connected in this circuit. star-connected choking coils at the bus-bars In order that the sensitiveness of the reand also with the grounded shell of the genlay should not fluctuate too much with the erator. This protective system is not satisfrequency but should remain fairly constant factory in so far as the relay, if very sensiwithin a certain range suificient damping tive, is liable to respond even when the has been provided. The ohmic resistance generator is sound, owing to the fact'that required for this purpose is indicated at 16. 75

,the sum of the third harmonics of the volt- As a matter of course this resistance might age waves generate currents in the conduc-- be contained in the resistances of the other tor between the neutral points of the genappliances in this circuit. It will be unerator and the bank of transformers or the derstood that instead of the illustrated choking coils. In order to prevent the retuning of the relay to the network fre- 80 sponse of the relay owing to these equalizquency other known systems might be eming currents it is necessaryl to keep the sen- ,ployed for the same purpose. sitiveness of the relay wit in certain limits. What I (31mm as y lnvelltloll According .to my invention the opera- 1. In a protective system for alternatingtion of the relay by the third harmonics is current generators having star-connected 85 35 id d b employing a. relay which can windings, a relay connected to the neutral only respond to currents the frequency of point of the generator adapted to respond hi h li ithin the her f the freonly to currents the frequency of which quency of the network. In this'manner it lies in the neighborhood of the frequency is possible to employ a sensitive relay in of the generator. 7

40 the known protective system of connection 2. In a protective system for alternatingdescribed in the introduction. current generators, a relay so connected to The drawing afiixed to this specification the generator as to be energized upon. the

and forming part thereof shows an examoccurrence of a fault therein, said relay invention. tothe frequency of the generator.

Referring to the diagram of connections 3. In a protective stem for alternatingshown it will be seen that the three-phase current generators, t e combination of a alternating current generator 1 is connected relay so connected to the generator as to. I to the bus bars 3 through aYtransformer 2. be energized upon the occurrence of a fault 100 The neutral point 4 of the winding of the therein, a resonance circuit for said relay generator -1, the primary neutral point of tuned to the frequency of the generatm' and ple of a protective system according to my being connected in a resonance circuit tuned so connected to'sald system as to be responsive to ground current flowing in said neu tral, said relay comprising contact memmal frequency of the system for actuating said contact members.

In testimony whereof I afiix my signature.

bers and resonant means tuned to the nor- WILHELM GAARZ. 

